1. Technical Field
The invention is related to the field of signal encoding for compressing the signal and subsequent decoding to reproduce the signal.
2. Related Art
The invention relates to a transmitting device for transmitting a digital information signal via a transmission medium, including:
an input for receiving the digital information signal,
an encoder for encoding the digital information signal and generating an output signal.
The invention further relates to a receiver for receiving a composite signal via a transmission medium, to a method of transmitting a digital information signal via a transmission medium, and to a record carrier carrying a digital information signal having portions which have been or have not been encoded by a given encoding method.
A transmitter and receiver of the type defined in the opening paragraphs is known from the AES preprint 4563 xe2x80x9cImproved Lossless Coding of 1-Bit Audio Signalsxe2x80x9d by Fons Bruekers et al, 103rd AES Convention (New York, US). The known transmitter is intended for efficiently reducing the bit rate for the transmission of a digital information signal. A composite signal thus obtained includes an encoded version of the digital information signal. On an average, the composite signal obtained by the known transmitter contains less bits than a composite signal in which the digital information signal has not been encoded.
It is an object of the invention to provide a transmitter and/or receiver which transmits a digital information signal with a smaller or at the most equal number of bits. The invention also enables more information to be stored on a record carrier.
To this end, a transmitter in accordance with the invention, further includes:
a controller for generating a control signal to be applied to the encoder, and the encoder generates portions of the output signal in the form of encoded portions of the digital information signal under the influence of a control signal of a first type, and generates portions of the output signal in the form of portions of the digital information signal under the influence of a control signal of a second type;
a first identification signaler for generating a first identification signal of a first type which indicates that the output signal possibly includes a portion of the digital information signal which has been encoded in the encoder, and a first identification signal of a second type which indicates that the output signal does not include any portions of the digital information signal which have been encoded by the encoder;
a second identification signaler for generating, for a portion of the digital information signal, a second identification signal of a first type depending on the control signal of the first type and the first identification signal of the first type, and a second identification signal of a second type depending on the control signal of the second type and the first identification signal of the first type;
a combiner for combining the output signal of the encoder, the first identification signal and, if the first identification signal is of the first type, the second identification signal so as to obtain a composite signal to be applied to the transmission medium.
In a receiver in accordance with the invention, a demultiplexer derives a first identification signal of a first type and a second type from the composite signal, and decodes a signal portion into a portion of the digital information signal and supplies the portion of the digital information signal depending on a control signal of a first type and supplies signal portion as a portion of the digital information signal in a substantially unmodified form depending on a control signal of a second type, and the receiver further includes:
a controller for generating the control signal for application to the decoder, which controller generates a control signal of the first type depending on the first identification signal of the first type.
A method in accordance with the invention includes the steps of:
generating a control signal;
generating portions of an output signal in the form of encoded portions of the digital information signal under the influence of a control signal of a first type;
generating portions of the output signal in the form of portions of the digital information signal under the influence of a control signal of a second type;
generating a first identification signal of a first type which indicates that the output signal possibly includes a portion of the digital information signal which has been encoded in the encoder, or a first identification signal of a second type which indicates that the output signal does not include any portions of the digital information signal which have been encoded by the encoder;
generating a second identification signal of a first type depending on the control signal of the first type and a first identification signal of the first type;
generating a second identification signal of a second type depending on the control signal of the second type and the first identification signal of the first type;
combining the output signal of the encoder, the first identification signal and, if the first identification signal is of the first type, the second identification signal so as to obtain a composite signal; and
applying the composite signal to the transmission medium.
A record carrier in accordance with the invention carries a digital information signal having portions which have not been encoded and other portions which have been encoded by using a given encoding method, and carries a first identification signal which is of a first type which indicates that the record carrier may carry a portion of the digital information signal encoded using the given encoding method.
The invention is based on recognition of the fact that by using an encoder, the number of bits required to transmit a digital information signal is not always reduced. In the encoder, some signals give rise to an output signal which requires more bits for the representation of the digital information signal than the digital information signal itself. In the device and the method in accordance with the invention, in order to preclude this increase, the representation having the smaller number of bits is transmitted together with an identification signal, which indicates whether or not the signal has been encoded by a given encoding method. A record carrier can store a maximum number of bits. If the record carrier is obtained using the method in accordance with the invention, it can store a composite signal with a larger digital information signal.